In multipoint videoconferencing, three or more endpoint terminals communicate with each other across a network. In the current telecommunications environment, multipoint conferencing is usually implemented over circuit-switched communication networks. Since connections are point-to-point in a circuit-switched network, a centralized resource, known as a multipoint control unit (MCU), is needed to link the multiple endpoints together. The MCU performs this linking by receiving multimedia (audio, video and/or data) information signals from endpoint terminals over point-to-point connections, processing the received information signals, and retransmitting the processed signals to selected endpoint terminals in the conference.
In the past, multipoint videoconferencing generally has been operated in an automated, unattended fashion whereby conference participants have been self-sufficient in the process of initiating and conducting a conference call. In such an automated unattended conference mode, an operator typically became involved only when a problem was encountered during the conference. The conference operator might be engaged by dialing #0 at the participant's terminal or by directly calling the operator via a separate telephone line. This is similar to the model used by many audio conferencing service providers in which two telephone numbers are assigned for a conference, one for the conference attendees and the other for the conference moderator to reach the operator.